The invention relates to a video apparatus delivering video signals, notably S-Video signals.
S-Video signals are a possible representation of video sequences consisting of a luminance signal (generally referred to as Y) and of a chrominance signal (C). S-Video signals are for instance generated by a S-VHS video cassette recorder (VCR) or by a DVD player having a S-Video output.
It is always desirable to superimpose images or characters, for instance menus, on the video sequence delivered by the video apparatus:this superimposition is called On-Screen Display (OSD) and is usually sent out of the video apparatus (for instance to a display) as three monochrome signals (RGB format) through a Scart connector.
Two solutions have already been proposed to output the S-Video signals:
in a first solution, a dedicated S-Video connector is used;
according to a second solution, two pair of pins of the Scart connector are used, specifically the pins conventionally used for the CVBS signal and the pins conventionally used for the red monochrome signal (R).
With the first solution, as the video signal representing the video sequence goes through the S-Video connector, the video signal can be transmitted, for instance to a display, even when the Scart connector is not used. The user would then be unable to view the menus generated as OSD.
When using the second solution, the conventional pins for the red monochrome signal are not available and the OSD cannot be displayed properly.
It is desirable for a video apparatus to deliver a video signal which can also transmit OSD information in any circumstance.
FIG. 3 of patent application JP 10-336 603 A proposes a video apparatus delivering YUV signals wherein a YUV signal representing an OSD picture is superimposed on a YUV signal from a NTSC encoder by an analog switch. However, this solution needs using an OSD circuit generating a YUV signal (or a signal easily convertivle to YUV), which is not conventional; or, when using a conventional OSD circuit generating analogue RGB signals, a costly dedicated RGB to YUV converter must be provided in addition.
The invention provides a video apparatus delivering video signals wherein OSD superimposition is realised in a cost effective way whatever the used OSD circuit, while keeping at the same time a good quality of superimposition, i.e. for instance without any colour hue.
The invention provides a video apparatus comprising a video source with a luminance output carrying a first luminance signal, an OSD circuit generating OSD signals and a fast-blanking signal, and a connector for delivering video signals, wherein a converter outputs a second luminance signal based on the OSD signals, wherein a first switch controlled by the fast-blanking signal selectively connects the converter or the luminance output to the connector, wherein the video source has a chrominance output carrying a chrominance signal and wherein a second switch controlled by the fast-blanking signal selectively connects the chrominance output or a circuit generating a constant chrominance signal to the connector.
According to prefered embodiments,
the constant chrominance signal is a constant voltage;
a voltage divider generates said constant voltage;
said OSD signals are three monochrome signals;
said converter is a resistor matrix network;
said connector delivers S-Video signals;
said connector is a Scart connector;
said connector is a S-Video connector;
said video source is a S-Video source;
said connector delivers S-Video signals and said video source is a S-Video source.